Bible Flashcards
(104 cards)
1
Q
Define Velocity
A
Velocity is the rate of change of displacement.
2
Q
Define work done by a force.
A
Force x distance moved in the direction of the force.
3
Q
Define the watt.
A
1 Joule (of work) per second.
4
Q
Define the force constant of a spring.
A
The force per unit extension of the spring. f=kx
5
Q
Define centre of gravity.
A
The point at which the entire weight of the body appears to act.
6
Q
Define moment of a force
A
moment = force x perpendicular distance to the pivot
7
Q
Define Acceleration
A
Acceleration is the rate of change of velocity.
8
Q
State the principle of moments
A
When an object is in equilibrium, the sum of the clockwise moments equals the sum of the anticlockwise moments.
9
Q
Define the term “couple”
A
Two equal but opposite forces.
10
Q
Define the torque of a couple.
A
Torque = one of the forces x perpendicular distance between the forces
11
Q
Define Power.
A
Power = work done/ time
12
Q
State the principle of conservation of energy
A
In a closed system, energy cannot be created or destroyed, only converted from one form to another.
13
Q
Define braking distance.
A
The distance travelled by the car after the brakes are applied until the car stops.
14
Q
State Hooke’s Law
A
The extension is directly proportional to the force applied, as long as the elastic limit is not exceeded.
15
Q
Define the YM of a material and state the condition when it applies.
A
- YM = stress/ strain
- It is obeyed so long as you do not exceed the elastic limit.
16
Q
Define density
A
Density = mass / volume
17
Q
Define a vector quantity and give one example
A
- A quantity with both magnitude and a direction.
- e.g. displacement, velocity, acceleration, force, weight…
18
Q
Define thinking distance.
A
The distance travelled by a driver from when the driver sees the problem till when the brakes are applied.
19
Q
Write a word equation for KE
A
KE= 1/2 x mass x speed^2
20
Q
Define the Newton
A
The force when a 1kg mass is accelerated at a rate of 1 m/s^2
21
Q
Newton units
A
N = kg m/s^2
22
Q
What is meant by “plastic deformation”
A
The material is permanently deformed when the force/stress is removed.
23
Q
Define a materials “elastic limit”
A
The material is permanently deformed when the force/ stress is removed.
24
Q
Define ultimate tensile strength of a material.
A
The maximum stress a material can withstand before breaking.
25
Define the speed of an object.
Speed is the rate of change of distance.
26
What does it mean to describe a material as "brittle"
A brittle material does not have a plastic region. It breaks at the elastic limit.
27
Define electrical resistivity.
(funny row) p=RA/L
- R= resistance
- L=length
- A=cross-sectional area
28
-Define potential difference/ Define electromotive force
OR
-Distinguish between the potential difference and electromotive force.
Potential difference= energy transferred per unit charge from electrical into another form (such as heat or light)
Electromotive force= energy transferred per unit charge into electrical energy from other forms (such as chemical or mechanical)
29
What is Kirchoff's First Law, and what quantity is conserved by it?
The sum of the total current into a junction equals the sum of the current out of the junction. The equivalent to a statement of conservation of charge.
30
What is Kirchoff's Second Law, and what quantity is conserved by it?
The sum of emfs is equal to the sum of the potential differences around a closed loop of a circuit. The equivalent to a statement of conservation of energy.
31
Define resistance.
R= potential difference/ current
32
Describe what is meant by the "mean drift velocity" of the electrons in the wire.
The average displacement/distance travelled by the electrons along the wire per second.
The electrons collide with a metal ion after travelling a short distance within the lattice, but over time, they slowly move in one direction through the metal lattice when there is a potential difference across the wire.
33
State the difference between the direction of the conventional current and electron flow.
Conventional current moves from positive to the negative side of a battery, whereas electron flow actual takes place from the negative side of the battery to the positive.
34
Define the kilowatt-hour.
A unit of energy equal to 3.6MJ, or 1kW for 1 hour.
35
State Ohm's Law
Potential difference is directly proportional to current, if the component is at constant temp (and other physical conditions remain constant).
36
Define power.
Power is the energy transferred per unit time.
37
Equation for power in joule getting when current flows
P=IV
38
Define the electron volt
1 eV is the energy transferred to an electron when it accelerates through a potential difference of 1 V
39
1 eV is equal to....
1.6x 10^-19 J E=QV
40
Explain the meaning of the term "internal resistance"
- In real batteries, some of the energy is transferred into thermal energy inside the battery itself. It behaves as if it had an 'internal resistance' that some of its voltage is dropped across.
- Therefore, E= V+Ir, where E=the emf of the battery, V= the potential difference across the circuit, I is the current in the circuit and r is the internal resistance of the circuit.
41
Describe what is meant by a plane polarised wave
The oscillations of the wave are in one direction only.
42
State the differences between a progressive and a stationary wave.
- A progressive wave transfers energy, a standing wave does not.
- A progressive wave transfers information, a standing wave does not.
- Every point on a progressive wave has the same amplitude. A stationary wave has nodes and antinodes.
- Every point on a progressive wave oscillates. A stationary wave has some points that do not move.
- All points in one wavelength of a progressive have different phase. All points in a stationary wave between nodes are in phase.
43
What does it mean if two waves are "coherent"?
There is a constant phase difference between the waves
44
Explain the term intensity.
Intensity is the power per unit area, perpendicular to the direction of energy transfer.
45
Define a longitudinal wave
The oscillations of the wave are parallel to the direction of energy transfer.
46
Define a transverse wave
The oscilations of the wave are perpendicular to the direction of energy transfer.
47
Define the work function
The energy required for an electron to escape the surface of a metal with the minimum energy.
48
Explain how the threshold frequency is connected to the work function?
A photon with less than the threshold frequency cannot cause an electron emission, so the work function is equal to the threshold frequency x Planck's constant
49
State the principle of the superposition of waves
When 2 or more waves meet at a point, the resultant displacement is the vector sum of individual displacements of the waves.
50
State what is meant by the photoelectric effect
The emission of a photon from the surface of a metal when photons of electromagnetic radiation are incident on the surface.
51
Explain what is meant by a progressive wave
A progressive wave if the transfer of energy as a result of oscillations.
52
State what is meant by the De Broglie wavelength of an electron
Electron wavelength depends on its speed/ momentum.
| mark scheme accepts the de broglie equation?
53
Define, with regards to wave motion, displacement, amplitude and frequency.
Displacement=distance moved from the equilibrium of a point on a the wave.
Amplitude= the maximum displacement of the wave.
Frequency= the number of oscillations passing a point per unit time
54
State properties of EM waves that aren't shared by other waves.
They can travel in a vacuum.
They all travel at the same speed in a vacuum 3x10^8
They are caused by accelerating charges.
They are oscillating electric and magnetic field.
55
Explain what is meant by the diffraction of a wave.
The wave fronts of a wave spread out after passing through a gap.
56
State an experiment that demonstrates and provides evidence that EM radiation can behave as a wave and as a particle.
Particle: Photoelectric effect
Wave: Young's slits
57
State an experiment that demonstrates and provides evidence that electrons can behave as a wave.
Electron diffraction through graphite film.
58
State Malus' Law
I=Io cos^2(feta)
Where Io is the max intensity of the incident polarised beam and feta is the angle between the polarisation of the polaroid and the polarisation of the incident polarised beam.
59
Explain how a standing wave is formed on a string with two fixed ends
- the incident wave is reflected at the fixed ends of the string.
- the reflected wave interferes with the incident wave.
- to produce a resultant wave with nodes and antinodes
60
Explain how light and dark fringes form in a Young's slits experiment
- Bright fringes form when constructive interference occurs and the waves add together to give a maximum amplitude at the screen
- This occurs when the path difference between the slits and the screen is an integer number of wavelengths when they arrive at the screen.
- Dark fringes form when destructive interference occurs and the waves subtract to give a minimum amplitude at the screen.
- This occurs when the path difference between the slits and the screen is an odd half integer number of wavelengths when they arrive at the screen.
61
Explain how to use a metre rule, a stopwatch and a tennis ball to determine an approximate value for the acceleration,g, of free fall.
- drop ball from a given height and measure time of fall.
- s=ut+ 1/2at^2 and u=0
- therefore the acceleration due to free fall, a= 2s/ t^2
62
Describe and explain how a seat belt reduces the force on a driver during the impact in an accident.
- the time taken for the driver to stop is longer.
- f =ma
- if the time taken to stop is longer, the acceleration of the impact must be smaller, so F must be smaller, as m remains the same
63
(Polymeric) Identify the type of material from the figure. Describe the properties of this material.
- Polymetric (e.g. rubber)
- The material is elastic; there is no strain when the forces are removed.
- The material displays "hysteresis"; more work is done on the material when loading than you get back as you unload the material.
64
(Brittle) Identify the type of material from the figure. Describe the properties of this material.
- Brittle (e.g. glass)
| - the material does not experience plastic deformation before it reaches its ultimate tensile strength and breaks.
65
(Ductile) Identify the type of material from the figure. Describe the properties of this material.
- Ductile (e.g. metal)
- the material experiences significant plastic deformation before it eventually reaches its UTS and breaks, so could easily be drawn into a wire.
66
How is the braking distance of a car affected when its mass increases? Assume driver uses the same breaking force.
- the braking distance would be longer.
- to come to a complete hault, work done by brakes =KE
- Therefore, force x braking distance= 1/2 x mass x speed^2
- so if the mass is bigger, the KE is bigger, and the breaking distance is prop to the KE, so the braking distance is bigger.
67
Explain how terminal velocity works.
- Originally, weight is greater than the drag, so the object accelerates downwards.
- Drag is proportional to v^2, so as the velocity increases, the drag increases.
- Weight is constant and drag opposes the motion, so the net force gets smaller.
- hence the acceleration gets smaller
- eventually, the object will be travelling so fast that drag is equal to the weight.
- here, the net force is zero, hence the acceleration of the object.
- hence, the object moves at constant velocity, which we call terminal velocity.
68
Describe an experiment to find the YM of a material. (apparatus)
- get a wire of the material fix it at one end and hang it over a pulley at the other end. get a range of masses in order to produce extension
- a micrometer and a metre ruler.
69
Describe an experiment to find the YM of a material. (readings)
- measure original length with ruler.
- measure the extension with the ruler as you hang different masses off a wire.
- measure the diameter of the wire with the micrometer.
- use W=mg with the known masses to calculate the weight applied.
- detail: use a long wire, longer then 2m
- detail: measure length in several locations and take an average.
70
Describe an experiment to find the YM of a material. (analysis)
- produce a graph of force against extension
- determine the gradient. define stress and strain.
- YM= stress/strain. Hence, YM= force x original length/ extension x area
- YM = gradient x original length/ Area
- Area= pie x r^2, r= half of diameter
71
What is ultrasound?
A longitudinal wave with a frequency greater than 20 kHz
72
What is the piezoelectric effect?
The material expands or contracts when a p.d. is applied across its opposite faces.
73
EM waves attenuate in matter : Simple scattering?
| - Basic Mechanisms?
The photon is scattered by an atomic electron.
74
EM waves attenuate in matter : Photoelectric effect?
| - Basic Mechanisms?
A photon is fully absorbed by an atomic electron, which is then ejected. Another electron falls into the hole this creates and emits a second photon with lower energy.
-30 keV
75
EM waves attenuate in matter : Compton scattering?
| - Basic Mechanisms?
A high energy photon knocks an electron out of an atom, causing the photon to lose energy scatter.
76
EM waves attenuate in matter : Pair production?
| - Basic Mechanisms?
A high energy photon transform into an electron positron pair
-1 GeV
77
Define acoustic impedence?
The density of the material multiplied by the speed of sound in the material.
78
What is impedance matching?
Using a coupling medium between the transducer and body with an impedance closer to that of the body tissue to reduce reflections.
79
What is a piezoelectric transducer?
A device that can convert sound waves into alternating voltages and can also convert alternating voltages into sound waves. We use them to produce ultrasound.
80
What are the advantages of ultrasound imaging?
- there are no known hazards (especially, no exposure to ionising radiation)
- good for imaging soft tissues as you can produce real time images.
- Relatively cheap and portable.
- Quick procedure during which the patient can move.
81
What are the disadvantages of ultrasound imaging?
- Ultrasound doesn't penetrate bone.
- Ultrasound cannot pass through air spaces, so can't produce images from behind the lungs.
- Can't give detail about solid masses.
- Can't give information about any solid masses found.
82
Describe the process of fission.
A slow moving neutron is absorbed by a large nucleus, causing it to split into two fragments (called daughter nuclei) and several neutrons.
83
Describe the conditions involved in fission reactor.
- Requires slow moving neutrons to trigger (hence a relatively low temp)
- Reaction is controlled by either absorbing or slowing the released neutrons.
84
Describe the process of fusion.
Two smaller nuclei moving quickly have enough KE to overcome the electrostatic repulsion between them, get to within around 3fm of each other and the strong force is able to fuse them into a single, larger nucleus.
85
Describe the conditions required for fusion
- Very hot to give particles the KE to overcome the Coulomb repulsion.
- Very high pressure and density to allow for enough random collisions to occur.
86
How can I perform an experiment to figure out what types of radiation are present in a radioactive source?
- Set up a geiger-muller tube and take a measurement of background radiation.
- Set up the source, and take a measurement of activity. Subtract background radiation from it.
- Place a piece of paper in between. Does the activity go down? If so, it has alpha in the radiation.
- Place a piece of aluminium in between. Does the activity go down significantly more than it did for paper? In which case beta particles are present in the radiation.
- Place a piece of lead in between. Does the activity go down significantly more than it did for the paper of the aluminium? In which case gamma rays are present in the radiation.
87
Describe nuclear fission and how the chain reaction is controlled.
- Fission is the splitting of a large nucleus into multiple smaller nuclei.
- Fast moving neutrons are released in this process.
- The neutrons are slowed down by the moderator...
- So they can be absorbed by other uranium nuclei...
- Causing further fissions. We call this a chain reaction.
88
What is binding energy?
The minimum external energy (usually given per nucleon) required to separate all the protons and neutrons in a nucleus. E=mc^2
89
What is the mass defect?
The difference between the total mass of the individual, separate nucleons and the mass of the nucleus. E=mc^2
90
Fuel rods: what are they made of and what do they do?
Made from uranium. This is where the nuclear fission actually takes place.
91
Control rods: what are they made of and what do they do?
Made from boron or cadmium. Absorb neutrons which slows the rate of the reaction. Can be lowered and raised to speed or slow rate of reaction.
92
Moderator: what are they made of and what do they do?
Made from graphite or heavy water. Slow down the speeds of neutrons in order to allow collisions to occur and increase the rate of reaction.
93
Shielding: what are they made of and what do they do?
Made from lead. Stops radiation from exiting the reactor and holds the reactor together.
94
What are Hadrons?
A non-fundamental particle made up of quarks. Quarks can be assembled in two possible configurations.: baryons, mesons.
95
What are Baryons?
Three quarks bound together. Examples include protons and neutrons.
96
What are Mesons?
A quark- antiquark pairing. Examples include pions and kaons.
97
What are leptons?
A group of fundamental particles. Including electron, muon, tau, electron neutrino, muon neutrino, tau neutrino.
98
What are gauge bosons?
A group of fundamental particles that are responsible for the force interactions in nature.
99
Describe the similarities between gravitational and electric fields?
-The field strength or force proportional to 1/separation^2 -both produce radial field.
100
Describe the differences between gravitational and electric fields?
- Gravitational field is linked to mass and electric field is linked to charge
- Gravitational field is always attractive whereas electric field can be either attractive or repulsive.
101
What evidence do we have for the big bang theory?
- The big bang theory predicts that all galaxies will be receding and that galaxy velocity is proportional to distance from Earth.
- Radiation from most galaxies (such as Virgo) shows increase in wavelength or red shift. This change in wavelength caused by motion of galaxy by the Doppler Effect.
- This is evidence that these galaxies are receding from Earth and supports the big bang theory.
- Some nearby galaxies, most notably, Andromeda show blue shift. This shows that these galaxies are approaching ours, and is due to attractive gravity, not cosmological effect.
- The Cosmic Microwave Background Radiation (CMBR) formed as gamma radiation at Big Bang.
- Galatic red shift over time has stretched it to microwave wavelength. The intensity is uniform in all directions and it corresponds to a temperature of 2.7K. (Very small) ripples in intensity corresponding to formation of first stars or galaxies.
- Its presence is further evidence for the big bang.
102
How is stellar parallax used to measure the distance in space?
Stellar Parallax is the apparent motion or displacement of a star relative to the position of more distant stars caused by the Earth's orbit around the Sun.
An angle of parallax of 1 arc second when displacement of Earth is 1 AU corresponds to distance of 1 pc.
Diagram pg 34 of bible.
103
Discuss the life-cycle of a star. (Birth)
- A nebula is a cloud of Interstellar dust and gas. It is drawn together by gravitational force/ gravity.
- This results in loss in (gravitational) PE, the KE of the gas and the temperature increases.
- Eventually, the temperature is such that fusion (of protons/ hydrogen nuclei) takes place.
- Energy is released in fusion reactions.
- A stable star is formed when gravitational pressure is equal to internal / gas / radiation pressure.
104
Discuss the life-cycle of a star. (Death)
- Stars swell in size. They become more luminous but lose temperature to become Red Giants, or Supergiants if the star is much larger than the sun.
- For Giants, the star eventually ejects most of its mass as a planetary nebula, which leaves a white dwarf.
- A white dwarf is a core / 'star' left behind after a red giant (has shed its outer layers)
- For supergiants, the gravitational pressure is such that it overwhelms electron degeneracy pressure and electrons and protons merge to form neutrons, forming a neutron star. This occurs if the stellar remnant has a mass greater than the Chandrasekhar Mass
- EVEN larger stars may collapse further into a blackhole.
